Stand alone uninterruptible power supplies (UPSs) have been used on many known computer systems, such as the IBM AS/400 (IBM and AS/400 are registered trademarks of International Business Machines Corporation). UPS systems available in the industry typically provide backup power to computer systems by running an inverter on batteries to generate AC power. These systems typically also provide the ability to communicate certain status and control information with the systems they backup via an interface. The interface may be used to determine the operational status of the UPS which may include an estimate of the remaining run time left before the energy stored in the battery is depleted and the AC output is turned off, i.e., a so-called "fuel gauge" indication. The fuel gauge information may or may not be of use to the system receiving backup power, depending on the application of the system. For instance, if the time required to restart the system after a power loss is not significant, either because the restart time is short or because no data is lost, for example, then that application may have no use for a prediction of run time remaining.
On the other hand, if the time to restart the system is large and/or a data loss exposure exists, then it is generally understood that it would be beneficial to bring the system to a controlled stop before backup power is lost, because doing so may minimize the time to restart the system, for example.
In the past, a simple "contact closure" interface has been used to communicate status information from the UPS to the computer system, e.g., an IBM AS/400. In addition, the necessary software to control system operation during a utility failure was used to provide backup support. This contact closure interface is also referred to herein as the "9-pin" interface, which refers to the size of the connector (9 pin D shell) but not the number of signals as seen below. A typical pin-out for this interface would include the following:
pin 5-ground PA1 pin 6-UPS BYPASS ACTIVE PA1 pin 7-UPS BATTERY LOW PA1 pin 8-UPS ON PA1 pin 9-UPS UTILITY FAILURE
The status signal "UPS UTILITY FAILURE" indicates to the computer system that the UPS is operating on batteries. Note that this 9-pin interface does not have the sophistication of reporting how long the batteries will be able to support the system load, i.e., the fuel gauge function. However, this capability was approximated through system parameters that the user can set to control system operation during a utility failure.
One of these system parameters is called "qupsdlytim" representing UPS delay time. This value, selected by the user, controls the amount of time the computer system will continue normal data processing before it starts a controlled shutdown. If utility power returns before this delay expires, the system operation continues normally. If the delay expires before utility power returns, then an irreversible shutdown process is started. Note that the user computes the amount of time it will take to complete a controlled shutdown, adds this to the run time desired and buys a UPS that supports that total time. The time required to shutdown the system in a controlled manner depends on the application, the size of memory, the number of disk arms, and other variables. Of course, UPS cost increases with support time required, but an underestimation could mean that a controlled shutdown may not complete, and a long restart will be experienced as a result. Furthermore, the calculation is only valid if the UPS batteries are fully charged and the load on the UPS is known. Consequently, if the system was subject to repeated outages without sufficient time to recharge the batteries, the calculations will be inadequate and the controlled shutdown may not complete. Therefore, a conservative approach to this calculation is used.
While the "UPS utility failure" signal, indicating battery operation of the UPS is obviously an important signal, any change of state of any of the interface signals can be detected and reported to the operating system support for possible action. These state changes may cause the generation of messages to a user specified queue, for example, so that user implemented routines can be kicked off and/or appropriate remedial action taken based on these messages.
For example, if a UPS goes off line for service, the user provided support routines may deactivate certain critical processing jobs that are risky to have running when the backup power system is unavailable. This kind of standard UPS support has been integrated into computer systems, such as certain models of the AS/400.
Of course, as the size, performance, and complexity of computers increases, the time to perform an orderly shut down of the computer after a utility failure is detected increases and the power requirements also increase. To ameliorate this and protect purchasers of the computer systems from the possible adverse consequences of a power failure, an integrated backup capability was built-in to certain models of the AS/400. This integrated backup system was designed to protect those users who choose not to purchase external UPS protection, and those users who did purchase an external UPS but wanted in addition an integrated failsafe CPM backup mechanism.
This integrated backup system was designed to power only the memory because the time for a complete shut down in systems with a large amount of memory was too long for the batteries that could be built-in to the computer system enclosure. This backup mechanism was therefore designed to a fixed, not customer alterable, 2 minutes for "ride-through" and CPM (continuously powered memory or continuous power mainstore) shutdown preparation time, followed by up to 48 hours of power for the memory only. The ride through time is a period of time during which the system continues to operate in anticipation that the utility power failure is temporary and can be ridden through until utility power is restored.
In a CPM shutdown, there is no time to write the changed contents of a mainstore memory to disk storage, so the contents of memory are preserved by continuously powering the memory. However, as mentioned, because the batteries for this integrated backup system had to fit in the computer system enclosure, the energy capacity was fixed by design, and thus there was no user control of the so-called ride-through time. This CPM backup support was automatic and worked without any user intervention.
However, as mentioned above, in addition to this integrated support, the computer system user might still want to purchase a UPS system to provide additional protection, e.g., to provide in addition the standard UPS backup ride through time before the CPM backup mechanism was initiated. Therefore, UPS status was still provided for through the 9 pin interface, as described above, while status from the internal integrated backup system was provided via unique signals so that the software support in the operating system could differentiate between status provided by the UPS from status provided by the integrated backup system. The signals from the integrated internal backup system are considered to be more important by the computer operating system, since they may be occurring because the batteries in the UPS, if present, have been exhausted, for example, and CPM backup needs to be started. Thus, in such a system with both UPS and integrated CPM backup, the processing for the integrated CPM backup system preempted any computer system processing related to the UPS backup.
The integrated backup system was later implemented as a custom modification of an industry UPS system, leading to the so called "26-pin" interface which is described in the copending patent application referenced earlier. It should be noted that this custom modification, or "under the covers" system as it is also referred to herein, provides the integrated CPM backup system functions, but does not provide a traditional UPS functionality.
The under the covers system was sized to provide 2 minutes of run time at normal system load while the system is prepared for CPM. Then the system is turned off and only memory remains powered, for up to 48 hours more. The standard 9-pin interface for connection to an external standard industry UPS is still available to a user, if the user desires more protection than is provided by this under the covers integrated CPM support, with the 9-pin interface functions as were already described above. That is, the additional ride through time, for example, that the standard UPS can provide before CPM backup processing is begun.
As should be apparent from the above, leading to the development of the under the covers CPM backup system, which is the subject of the copending application referenced above, was the problem that as memory capacities of many computer systems grow, typical traditional UPS hold-up times (around 15 minutes) no longer support the time required to write the contents of the mainstore memory to a nonvolatile media, such as disk storage, for a controlled shut-down of many systems with large memories. The standard stand alone AC--AC UPS did not provide an effective power backup solution for many computer systems with a large memory, and a need existed for an improved method for providing backup power for system memory providing a continuously powered memory (CPM) function. The related copending application was designed to meet this need by providing a method and apparatus for providing backup power for a system memory, implemented in a modified uninterruptible power system (UPS) for a computer system to thereby provide a continuously powered memory CPM function.
The system according to the copending application, will now be described in more detail with reference to FIGS. 1 and 2. FIGS. 1 and 2 are block diagram representations of an exemplary computer or data processing system, and an embodiment of the power supply system of the copending application, respectively. A computer or data processing system is generally designated by the reference character 100. As shown in FIG. 1, the computer system 100 includes a central processor unit (CPU) 101, a read only memory 102, a random access memory or system mainstore memory 104, a display adapter 106 coupled to a display 108. The CPU 101 is connected to a user interface (UI) adapter 110 which is connected to a pointer device (and keyboard) 112. The CPU 101 is further connected to an input/output (I/O) adapter 114, which is connected to a direct access storage device (DASD) 116 and a tape unit 118. The CPU 101 is also connected to a communications adapter 120 providing a communications function with external devices and/or systems, for example.
With reference to FIG. 2, the power system according to an exemplary embodiment of the copending application, is designated generally by the reference character 148. The modified uninterruptible power supply (UPS) 150 includes an AC output and a DC output, an inverter circuit 166, one or more batteries 162, and an interface 154 to the system power supply 156. The inverter circuit 166 supplies AC power to the AC output of UPS 150. The at least one battery 162 supplies DC power to the DC output and to the inverter circuit 166. The control interface block 168 enables the inverter circuit 166 to initially supply AC power to the system power supply 156 via the AC output upon detection of a utility power loss and then, after a predetermined period of time, activates the DC output switch 164 to supply DC power to the system memory 104 via the system power supply 156, and disables the inverter circuit 166 to stop the initial supply of AC power to the system power supply 156.
The modified UPS 150 is connected to a panel and system power control network (SPCN) interface block 152 via the 26-pin UPS external interface connector 154, and to system power supply 156 and CPM voltage regulator 158 through this connector 154. A DC (direct current) voltage output from battery 162, e.g., +48V, is selectively fed into the power supply 156 via the 26-pin connector 154, in particular, to the CPM voltage regulator 158.
Regulator 158 selectively receives the DC voltage output from the modified UPS 150 and provides a set DC voltage output, such as a +3.3V output which is used to keep the system memory 104 powered during the time CPM is required. The +3.3V output of CPM voltage regulator 158 is applied to a first input of an OR block 160 connected to the system memory 104. A second 3.3 Volt input to the OR block 160 is provided by the system power supply 156 which normally supplies power to the system memory 104 when utility power is present. The CPM voltage regulator 158 provides power to the system memory 104 when utility power is lost, as will be described below.
As mentioned, the modified uninterruptible power supply (UPS) 150 includes one or more batteries 162 selectively providing the predetermined DC battery voltage output to the CPM voltage regulator 158, and this is done via a switch 164. The DC-to-AC inverter circuit 166 and the switch 164 are operatively controlled by the system power control function 152 using the control interface block 168 of the modified UPS 150.
During normal operation, a utility AC input to the modified UPS 150 is coupled by an OR functional block 170 to an AC input of the system power supply 156. Upon detection of a utility power loss, the modified uninterruptible power supply (UPS) 150 initially supplies AC power to the power supply 156 with the DC-to-AC inverter circuit 166, and then, after a predetermined period of time, for CPM shutdown preparation, stops supplying AC power, and instead supplies DC power to the system memory 104 directly from the battery 162, through the switch 164, the connector 154 and the CPM voltage regulator 158 of the system power supply 156. This DC power provides for continuously powering the memory, i.e., CPM.
The panel and system power control network (SPCN) determines when the predetermined period of time of utility power loss has elapsed, and then sends a DC On Command and an inverter Disable Command to the modified UPS 150 through interface 152 to control interface block 168. The external interface connector 154 is arranged to allow the use of the CPM shutdown capability with an external modified stand-alone uninterruptible power supply UPS configured for use as a CPM system. The modified UPS 150 is thus being used for CPM backup operation, and not traditional UPS functions.
The power system 148 is designed so that once a CPM control state is established by the system 100, all power can be removed from the system control circuitry. This makes essentially all power from the battery 162 available to memory 104. In addition, the power system 148 is designed so that its connecting cable connector 154 cannot be interrupted as a condition to turn on the DC output of UPS 150 via switch 164.
In operation, the system progresses through several operational states, which are now described. In state 1, the system 100 and modified UPS 150 are completely unpowered and inverter 166 is disabled, occurring at installation and any time utility power is removed after the system 100 is powered off, for example. Restoration of utility power causes a transition to state 2, where the modified UPS 150 has applied AC power to the system 100 with the system 100 turned off and inverter 166 disabled.
State 2 is the normal powered off state of the system 100. If a utility power failure occurs at state 2, the system 100 returns to state 1, the inverter 166 is not started, the DC output is not turned on, and the system 100 loses AC power. When the system is turned on in state 2, a transition to state 3 occurs, the normal powered on state of the system 100, where the modified UPS 150 is passing through AC and battery DC outputs of modified UPS 150 are turned off and the inverter 166 enabled.
When the system 100 is turned off in state 3, a transition to state 2 occurs. When a utility power failure occurs in state 3, which is signaled by a UPS utility failure signal, it causes a transition to state 4. In state 4, the system 100 is on and the modified UPS provides AC power to the system 100 with the inverter circuit 166, while the DC power from modified UPS 150 is off. If the utility power returns within a predetermined time period, for example within 30 seconds while in state 4, a transition back to state 3 occurs.
If the utility power is not restored within the predetermined time period, the system 100 makes a transition to either state 1(OFF) or a state 5. The system 100 makes a transition to the state 1 when conditions require a power off disabled so that the DC output will not be started. Otherwise, when conditions permit a power off enabled, the system 100 makes a transition to state 5 where the modified UPS DC power is turned on and applied to the CPM regulator 158 of the power supply 156.
In state 5, the inverter circuit 166 is off so that no AC power is provided to the system 100 and the interface signals are controlled by pull down resistors, as in state 1. The modified UPS 150 shuts down its logic to maximize the energy available to the system 100, with the DC output providing power to maintain the contents of the system memory 104, i.e., CPM operation.
Restoration of utility power in state 5 causes a transition to state 6. In state 6, the modified UPS 150 powers on and applies AC power to the already powered off system 100. Since the system 100 may remain powered off indefinitely, state 6 may exist indefinitely. The DC output of modified UPS 150 is maintained active to keep the system memory 104 powered. In state 6, modified UPS 150 maintains the DC output by utilizing the restored utility power for charging the battery 162.
The system power control network interface 152 determines that CPM is enabled in state 6 and the DC on interface signal is maintained in its default active state, so the modified UPS 150 does not turn off the DC output to CPM regulator 158. However, if a utility power failure occurs while in state 6, system 100 makes a transition to the state 5.
The normal transition from state 6 to state 3 results from a system power on operation. After the system 100 has successfully powered on and enabled the inverter circuit 166, the DC output is turned off and the memory 104 is powered by the normal operation of system power supply 156.
Connections for the 26-pin modified UPS external connector 154 are defined as follows in Table 1 below:
TABLE 1 ______________________________________ Position Description ______________________________________ 1,2 +48 VDC CPM 3,5 Gnd 4 N/C 6 -UPS Bypass 7 -UPS Battery Low 8 -UPS On 9 -UPS Utility Fail 10,11 +48 VDC CPM 12,15 Gnd 13 N/C 14 +Battery Test 16 -DC On 17,19 Gnd 18 +Inverter enabled 20,21 Gnd 22 -Status Bit 1 23,25 Gnd 24 -Status Bit 2 26 -Status Bit 3 ______________________________________
Exemplary logical interface outputs are shown as follows in Table 2:
TABLE 2 ______________________________________ -UPS Bypass Active no connect or inactive -UPS On grounded in the UPS 150 to indicate a UPS is present -Battery Low a low level indicating the battery 162 may not contain sufficient energy to sustain a two minute AC outage -Utility Failure a low level indicates utility power has been lost and the UPS 150 is providing energy from its batteries 162 via the inverter circuit 166 ______________________________________
Exemplary logical interface status bit (1-3) outputs providing encoded to the system 100 are shown as follows in Table 3:
TABLE 3 ______________________________________ State Description ______________________________________ 000 UPS Normal, Inverter Enabled 001 Battery Test Accepted 010 Battery Test Rejected 011 CPM defective 100 UPS Battery Defective 101 UPS Defective 110 overload 111 UPS Normal, Inverter Disabled ______________________________________
Exemplary logical interface status inputs are shown as follows in
Table 4:
TABLE 4 ______________________________________ +Inverter Enabled A high level enables the UPS to provide AC to the using system at the next loss of utility power. A low level causes the UPS to disable the inverter so that AC is removed or can not be provided to the using system from the batteries. -DC On A high to low transition on this signal while +Inverter Enabled is active, activates the DC output (+48v) of the UPS. +Battery Test Request A high level request to the UPS to perform a battery test. ______________________________________
As mentioned above, systems such as the AS/400 computer system benefit from a Continuously Powered Memory (CPM) backup system when memory sizes reach a point where a conventional UPS cannot backup the system while all changed pages are written to permanent storage. This type of backup system was initially added in the form of an integrated battery backup system, described above, that provided full backup for 2 minutes while the software prepared the system for CPM and then 48 hours of backup for the memory only. The modified UPS power system providing CPM backup functionality was developed and disclosed in the copending application, referenced above.
However, a need exists for an enhancement to the previously described solutions which could combine both typical/standard UPS functions and the CPM functions described above, in one external stand-alone piece of equipment. This would provide both the CPM operation and standard UPS operation without the need of having both the integrated CPM functionality in one device, and an additional external UPS device.
Further, as noted above, in the industry standard UPS there is a so called fuel gauge capability which gives an indication of the run time remaining at current load so that equipment can anticipate when a total loss of power will occur. However, in the computer systems such as those described above, a need exists for both a period of UPS run time, and also a period of continuously powered memory (CPM) operation. The typical standard UPS fuel gauge function, however, does not take both of these two factors, UPS run time and CPM, into consideration.
Therefore, a need exists for an integrated UPS and CPM power system which provides a fuel gauge function that takes both UPS and CPM operation times into consideration.